| The herbicide atrazine is one of the widely used pesticides,which has caused serious pollution of surface water and soil in recent years.Bioremediation is more advantageous than other methods,but it is not easy to fix and recover degraded bacteria when added to water.In order to prevent large loss of engineering bacteria,this study used mycelium pellets and degraded bacteria to form an immobilization system,analyzed the correlation between mycelium pellets immobilization and changes in the structure of bacteria,investigated the degradation and utilization performance of the system,and screened out high-efficient atrazine degrading strains,providing available resources for atrazine biological treatment.In this study,the mixed culture was enriched from topsoil of maize field after longterm application of atrazine.After two-stage domestication,atrazine at a concentration of 50 mg/L could be completely removed by bacteria at about 8h.According to the method of first culture and then adsorption,the functional flora was fixed on the mycelium pellets of Aspergillus niger Y3,the formation effect of the immobilized mixed system was characterized and analyzed,and the stability changes of the mycelium pellets were investigated.The immobilization system of mycelium pellets has good stability,with the integrity coefficient remaining above 92%.High-throughput sequencing technology was used to analyze the community structure changes of environmental flora before and after acclimation(T,HJ)and mycelium pellets mixing system(HQ),the community composition was different before and after domestication,the abundance of bacteria in sample T was high,but only 7 species abundance increased significantly after the domestication,which Paenibacillus largest rise in abundance,at 26.31%,followed by Pseudomonas and Paenarthrobacter;A total of 12 genera showed significant differences before and after adsorption,among which the genera that increased or decreased the most were Paenarthrobacter and Pseudomonas respectively.Atrazine in water was taken as the degradation target,and the optimal treatment conditions were as follows: bacterial liquid(OD600=1)volume 30 mL,pH=7,adsorption time 6-8 h,temperature 30℃.By comparing and analyzing the treatment efficiency of the mixed system and the advantages of adding mycelium pellets,the bacteria-coupled system can effectively remove 100% atrazine.The reuse performance of mycelium pellets was investigated,and the result show that perfect.The atrazine removal rate of mixed mycelium pellets remained above 90% after 6 cycles of use.Three atrazine degrading bacteria were selected from the functional flora as WL-1,WL-2 and WL-3.After morphological characteristics and 16 S rDNA sequence identification,the preliminary identification of WL-1 is Agrobacterium tumefaciens genus,WL-2 and WL-3 are Arthrobacter sp.To explore the degradation efficiency of the three strains on atrazine,atrazine concentration was set at 50 mg/L,the removal rate of WL-1 reached 68.4% at 24 h,and that of WL-2 and WL-3 reached 100% at 4 h and 5 h,respectively.Compared with other atrazine degrading strains,WL-1 is more advantageous than other strains of the same genus,and WL-2 and WL-3 have higher removal efficiency,which can realize the efficient removal of atrazine. |
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